1. Field Of The Invention
The present invention relates to apparatus for facilitating the machining of cams at a cutting speed which remains constant.
The invention relates in particular and advantageously to the trueing of cams on a grinder provided with a wheel removing only a machining allowance of several tenths of a millimeter from the work-piece. In this case, the approximate shape of the contour of the work-piece has been obtained previously by another machining method, for example by turning or milling.
2. Description Of The Prior Art
For this method of machining, a cam is mounted between points on the geometric axis as a template referred to as the "master cam". This master cam is a reproduction member of appropriate shape which rests on a roller which is free to rotate but which is itself set in rotation in order to bring about a pivotal movement of the arrangement comprising the master cam and the cam whereas the wheel generates the desired shape on the cam.
In view of the fact that the master cam and the cam rotate at a constant speed without taking into account variations in the radius of the cam, it follows that the cutting speed of the wheel is variable. Thus, in certain areas where the cutting speed is low, the metal is easily removed by the wheel, whereas in certain areas where the cutting speed is very high, the wheel does not have time to remove the metal and the work-piece flexes in front of the wheel. In fact, the axis of rotation of the work-piece, which is not infinitely rigid, moves back in front of the wheel which results in a deformation of the contour machined.
By unduly increasing the number of rotations of the work-piece in front of the wheel, it is possible to lessen this defect, however, without eliminating it completely. This method is troublesome, since it increases the trueing time which justly constitutes one of the important parameters of the manufacturing cost of the cam.